1. Field of the Invention
This invention relates to a vehicle-to-vehicle distance calculation apparatus and method.
2. Description of the Related Art
Calculation of vehicle-to-vehicle distance is important in order to prevent vehicular accidents. In order to achieve this, systems are available such as one that detects, say, the license plate of the vehicle traveling ahead and calculates the distance to that vehicle (Patent Documents 1 to 3). Various other approaches have been considered as well (Patent Documents 4 to 9).
[Patent Document 1]: Japanese Patent Application Laid-Open No. 61-155909
[Patent Document 2]: Japanese Patent Application Laid-Open No. 2007-15525
[Patent Document 3]: Japanese Patent Application Laid-Open No. 6-229759
[Patent Document 4]: Japanese Patent Application Laid-Open No. 2011-150417
[Patent Document 5]: Japanese Patent Application Laid-Open No. 2010-19589
[Patent Document 6]: Japanese Patent Application Laid-Open No. 7-111712
[Patent Document 7]: Japanese Patent Application Laid-Open No. 11-166811
[Patent Document 8]: Japanese Patent Application Laid-Open No. 2002-327635
[Patent Document 9]: Japanese Patent Application Laid-Open No. 2005-321872
However, all of the techniques set forth in Patent Documents 1 to 9 are unsatisfactory in terms of lowering cost of development and shortening processing time. In Patent Document 3, for example, vehicle-to-vehicle distance is calculated using the width of a vehicle in an image, but since vehicle width differs from vehicle to vehicle, this makes it necessary to store the width of all vehicles in advance. Whenever a new vehicle is made available for sale, therefore, it is necessary to store the width of the vehicle and, as a consequence, development cost cannot be reduced. Further, since it is required that detection relating to all vehicles be performed when calculating vehicle-to-vehicle distance, processing time cannot be shortened.